Non-Statistical Effects in Neutron Capture

There have been many reports of non‐statistical effects in neutron‐capture measurements. However, reports of deviations of reduced‐neutron‐width (Γn0) distributions from the expected Porter‐Thomas (PT) shape largely have been ignored. Most of these deviations have been reported for odd‐A nuclides. Because reliable spin (J) assignments have been absent for most resonances for such nuclides, it is possible that reported deviations from PT might be due to incorrect J assignments. We recently developed a new method for measuring spins of neutron resonances by using the DANCE detector at the Los Alamos Neutron Science Center (LANSCE). Measurements made with a 147Sm sample allowed us to determine spins of almost all known resonances below 1 keV. Furthermore, analysis of these data revealed that the Γn0 distribution was in good agreement with PT for resonances below 350 eV, but in disagreement with PT for resonances between 350 and 700 eV. Our previous (n,α) measurements had revealed that the α strength function...